Gene transfer technologies offer the prospect of novel therapeutic approaches to treat or prevent cancer. Combined with advances in molecular medicine, cell therapies, immunotherapy, array-based diagnostic technologies and pharmacogenomics, gene transfer and cell engineering are poised to play an important role in several aspects of the management of cancer patients. The transition from a laboratory-based hypothetical therapeutic strategy to clinical research depends on safe and efficient transduction of patient cells, quantitative analyses of gene transfer efficiency and transgene expression, and other services provided by the Gene Transfer and Somatic Cell Engineering Facility, abbreviated hereafter GTS. The GTS is crucial for the implementation of clinical trials developed from gene transferrelated research carried out at MSKCC. Depending on the nature of the research, the role of the Facility is centered on vector production, patient cell transduction, or both. The specific aims of the GTS are to perform the following: ex vivo transduction of patient cells, production of clinical grade plasmid DNA and retroviral vectors, developmental work relating to transduction and vector production, and molecular analysis of gene transfer efficiency and transgene expression in patient cells and tissues. The role of the Facility is not confined to the clinical phase alone. The GTS plays three important functions in the preclinical phase of specific projects. One is support in designing and eventually generating onco-retroviral and lentiviral vectors. Another is to supply large amounts of vector or genetically modified cell populations for preclinical studies. The third is a service development function that is indispensable in developing standard operating procedures (SOPs) that are essential for IND applications and the implementation of clinical trials. Importantly, the GTS comprises an internal Quality Assurance (QA) and Quality Control (QC) unit. QA and QC activities serve to ascertain due quality of processes and procedures in three distinct areas: plasmid DNA manufacture, retroviral vector production, and somatic cell engineering. The GTS thus plays an essential role in providing expertise, facilities, and a regulated environment that neither individual research groups or clinical units can develop on their own.